Green L L, Jakobovits A
Abgenix, Inc., Fremont, California 94555, USA.
J Exp Med. 1998 Aug 3;188(3):483-95. doi: 10.1084/jem.188.3.483.
The relationship between variable (V) gene complexity and the efficiency of B cell development was studied in strains of mice deficient in mouse antibody production and engineered with yeast artificial chromosomes (YACs) containing different sized fragments of the human heavy (H) chain and kappa light (L) chain loci. Each of the two H and the two kappa chain fragments encompasses, in germline configuration, the same core variable and constant regions but contains different numbers of unique VH (5 versus 66) or Vkappa genes (3 versus 32). Although each of these YACs was able to substitute for its respective inactivated murine counterpart to induce B cell development and to support production of human immunoglobulins (Igs), major differences in the efficiency of B cell development were detected. Whereas the YACs with great V gene complexity restored efficient development throughout all the different recombination and expression stages, the YACs with limited V gene repertoire exhibited inefficient differentiation with significant blocks at critical stages of B cell development in the bone marrow and peripheral lymphoid tissues. Our analysis identified four key checkpoints regulated by VH and Vkappa gene complexity: (a) production of functional mu chains at the transition from the pre B-I to the pre B-II stage; (b) productive VkappaJkappa recombination at the small pre B-II stage; (c) formation of surface Ig molecules through pairing of mu chains with L chains; and (d) maturation of B cells. These findings demonstrate that V gene complexity is essential not only for production of a diverse repertoire of antigen-specific antibodies but also for efficient development of the B cell lineage.
在缺乏小鼠抗体产生能力且用包含人类重链（H）和κ轻链（L）基因座不同大小片段的酵母人工染色体（YAC）进行工程改造的小鼠品系中，研究了可变（V）基因复杂性与B细胞发育效率之间的关系。两个H链片段和两个κ链片段中的每一个，在种系构型中都包含相同的核心可变区和恒定区，但含有不同数量的独特VH基因（5个对66个）或Vκ基因（3个对32个）。尽管这些YAC中的每一个都能够替代其各自失活的小鼠对应物，以诱导B细胞发育并支持人类免疫球蛋白（Ig）的产生，但在B细胞发育效率方面检测到了主要差异。具有高V基因复杂性的YAC在所有不同的重组和表达阶段都恢复了高效发育，而具有有限V基因库的YAC则表现出低效分化，在骨髓和外周淋巴组织中B细胞发育的关键阶段存在明显阻滞。我们的分析确定了由VH和Vκ基因复杂性调节的四个关键检查点：（a）从前B-I期向后B-II期转变时功能性μ链的产生；（b）小前B-II期的有效VκJκ重组；（c）通过μ链与L链配对形成表面Ig分子；以及（d）B细胞的成熟。这些发现表明，V基因复杂性不仅对抗原特异性抗体的多样化产生至关重要，而且对B细胞谱系的高效发育也至关重要。
